Conventionally these types of working units are driven mechanically. If these attachment devices for a tractor or agricultural devices are pulled by a tractor, the working units are connected by a mechanical drive line to a power take-off shaft of the tractor. The power take-off shaft is driven by the main drive, generally the tractor internal combustion engine.
In self-propelled agricultural working devices, the working units are driven directly by the main drive. Hydraulic drive systems are also known, in which the main drive drives a hydraulic pump, which serves as the hydraulic pressure source. Via hydraulic lines, hydraulic motors are driven, which again drive the working units.
These conventional drive systems have a multitude of mechanical drive components, which are dimensioned according to the to be transmitted torque. This leads to large and heavy drive systems. Therefore, the assembly of the drive components is cumbersome.
Small loads electrical motors have been used to drive self-propelled vehicles. The motors are connected to the vehicle electric system. These vehicle electric systems, however, generally only generate a nominal battery voltage of 12 Volts and a generator nominal voltage of 14 Volts. This voltage, however, is insufficient to drive electrical loads of drive units of agricultural devices. The electrical loads of the agricultural devices are too high.